inboard brakes

[Steven]

hi,

I don't know really if it's forbidden, but suppose it isn't... would it not be interesting to use inboard brakes in F1 cars. I suppose at the front would be a decent option.

Let's just assume we put the font brakes inboard... you would get front wheels that weigh less, so less unsprung weight. Furthermore you might try to open up the nose to let cooling air in for the brakes.

The only question I ask myself is maybe inboard brakes aren't used anymore because the need of an extra bar to connect the chassis with the wheels? It may also be a serious "driveshaft" as it has to resist quite some torsion under braking.

What do you think?

[manchild]

I’ve been thinking it over a lot -years ago and the only problematic thing seam to be “brakeshafts” and joints necessary for their implementation. Discs could be bigger and cooling could be better but aero drag would increase. It would also require increased length of chassis for certain amount.

Rear inboard brakes have been used some 30 yrs ago on Lotus.

[Scuderia_Russ]

I remember seeing an old Tyrell driven by Martin Brundle at Goodwood last year that had inboard rears out in the airflow. The 014 I think.

[manchild]

http://www.atspeedimages.com/csrg_2004/ ... brakes.jpg

[Apex]

I think that in the days of steel (heavy) breaks it may have been something to try out, but i feel that with todays carbon breaks the percentage gain in terms of unsprung mass is not as high as it was.

I remember a few years ago when the benetton had a diff between the front wheels to prevent/reduce lock-ups during breaking it was not really a success due to the added drag and mass and complexity.

Where could you put these disks? Would it not get in the way of the underbody airflow? Well I feel that putting them inside the rim is the perfect place because there is not a lot of space to go around in an F1.

If we consider coolong for a second, again it may have been feasible back in the day of steel breaks - but now with carbon there is even a cooling reserve, since the breaks need to be at an elevated temp.

What do you guys think?

[Monstrobolaxa]

IMO opinion the usage of inboard brakes brings the disavantage of having the drive/brake shaft being twisted in oposite directions (direction depending on what you're doing acelerating or braking)....this would probably no be a fantastic idea for the shaft! A drive shaft is twisted in only one direction....having it twisted in both directions would probably weaken it....in the long run! And to prevent it from fatigue due to the twisting momentum in both directions it would have to be thicker....bringing more weight!

[Steven]

I really think it's worth a try, but it could have been more interesting with the old low noses.

One more thing that comes to my mind may be security problems. At the moment there is nothing else then some suspension parts and the nose cone in front of the driver's feet... so it may be a problem to fit the brakes in without having to increase the crash structure's strength a lot.

Anyway Monstro... stress in both directions?? Brakes aren only stressing the brakeshaft in a rearward direction. I don't really think that a forward stress during acceleration (thus caused by the moment of inertia of the brake discs) is that a big factor. At least that's what I think.

[manchild]

I really think it's worth a try...

… and you could have two discs close to each other with one big common caliper with air circulating not only trough discs but also between them

[Monstrobolaxa]

Anyway Monstro... stress in both directions?? Brakes aren only stressing the brakeshaft in a rearward direction. I don't really think that a forward stress during acceleration (thus caused by the moment of inertia of the brake discs) is that a big factor. At least that's what I think.

Rear inboard brakes are applied on the drive shaft....so it would receive torsion in one direction under aceleration.....and torsion in the other direction under braking! (now do you understand what I was saying? )

When having the brakes "inside" the wheel assembly the braking force is applied directly onto the wheel/tire...while the drive shaft one receives a torsioning momentum in the direction of aceleration (positive...to the front)....and doesn't really receive too much torsion while braking!

When having the brakes inboard....when acelerating the ddrive shaft will "drive" the wheels....and will rotate in one direction....when braking the braking force will be applied in the oposite direction of the rotation....this oposite force direction will be transmitted through the drive/brake shaft to the wheel......in this case you'll have alot of torsion in both directions! While in the other case (outboard brakes) you only have a big amount of momentum in one directio!

[RH1300S]

It's always hard to comment on these things with a limited knowledge base, but he's a try anyway.

Inboard rears, easier to justify because you already have a drive shaft - but presumably the torque created by the brakes is much greater than from acceleration, so this item would need to be stronger/heavier than it is (not forgetting the reversed loads already discussed - just twist a pencil between your fingers to re-assure yourself which way they work ). Inboard rear brakes would surely interfere with the size/shape of the diffuser (maybe that's why they moved outboard again in the 1980's?).

Inboard fronts - you are adding an extra component (again would need to be very strong as the fronts still do most work). Then you would need to house and cool the brakes in the nose, making the nose wider. As far as I understand the air-flow between the wheel and the nose is critical to the performance of the rear of the car, so you probably compromise this for a small improvement in un-sprung weight. By adding a front driveshaft, you had a little to rotating masses (more spinning stuff to stop).

What will all that heat do to stuff in the cramped nose area - dampers/hydraulic fluid/power steering (driver's feet).

All in all, with race tracks being much smoother than in the 1960's and carbon brakes being very light, easy to cool (and compact enough to tuck into a wheel) the added complication and compromise elsewhere will be less than the gains from reducing unsprung weight.

A little add-on thought - I expect getting rid of heat from the outboard wheels is much easier than from the nose area and adding another heat source around the engine/gearbox cannot be a great idea.

Final one - - I understand that the heat from the brakes is pretty handy for heating tyres.

[Monstrobolaxa]

Inboard rears, easier to justify because you already have a drive shaft - but presumably the torque created by the brakes is much greater than from acceleration, so this item would need to be stronger/heavier than it is.

This is what I was saying....in a simpler way!

[manchild]

...(maybe that's why they moved outboard again in the 1980's?)...

I think that it was due to switching to CF brakes - heat they generate is much greater than with steel discs...

[StiK]

How do you know that the loads involved in accelerating a F1 car are bigger than the ones involved in stopping it? I would say that at first glance it would be so, but when accelerating, weight is transferred to the back and all acceleration is done by the rear wheels which could be as much as 1.5-1.7 Gs. When braking at high speed say 300Kph, high downforce configuration is used, a F1 car decelerates at about 5 Gs. 1G is from aerodynamic drag.The remaning 4Gs are from the brakes. When braking, weight is transfered to the front so a configuration of about 60-40 would give 2.4Gs at the front and 1.6Gs at hte back. This implies that the loads involved at the back are aprox the same for accelerating and braking.
As mentioned before an inboard rear brake would have to endure efforts in both ways which could be a problem but i think it wouldn't need much more because actually when shiffting down too fast an F1 car can lock the rear wheels quite easily. Im not saying that this implies that they are strong enough to withstand the efforts of both acceleration and breaking but that engineers have to account for this when projecting the shafts and that it would not require much reenforcement.

StiK

[DaveKillens]

Inboard brakes enjoyed a brief period of use in Formula One, but their future and confidence died the Lotus 72. http://www.ddavid.com/formula1/lotus72.htm
Jochen Rindt died in a possible front shaft failure that totally destroyed confidence in the design. Ever since then, designers have placed the brake assembly on the upright, as close to as possible, and with as few parts to go wrong.
Technically, inboard brakes promise new and innovative suspension options. I do like the idea of having the almost all of the braking forces fed through a shaft instead of the suspension components. Additionally, you would have very hot components within inches of a driver's feet. A comfort and safety issue. But from a safety standpoint, it's just one more component to go wrong. And when those components are a very important part of the safety package, you can't afford to err.

[RH1300S]

What I think I said was that the loads stopping it are bigger than acceleration - as you demonstrate. I don't know the brake force distribution of an F1 car 5g will send a lot of weight forward during braking (at first, then tapers off as you lose downforce) - if 60/40 is a good guess, then what you are saying is that the rear shafts may be close to the strength required and the front ones would probably need to be stronger.

Driveshaft strength is a bit academic as the other arguments seem to show the inboard brakes don't carry the advantages the used to.

Also, we must not lose sight of the unsprung weight/sprung weight ratio - when a car is carrying a lot of downforce on it's sprung mass - then this ratio becomes more favourable so the returns in reducing unsprung weight must diminish (apart from anything that reduces rotating mass of course).

As an aside, I have been trying to think of F1 cars with inboard FRONT brakes - Lotus 72 had them at some stage. I know this allowed Colin Chapman to use soft compound rubber as it was kept cooler and worked less hard by the arrangement. Can't think of any others........